It was late evening, and the table had been set under the fly of the main tent, used by the girl. It was the quiet hour of evening prayer. Sheep boys were driving their flocks homeward for the night along the road a short distance away. There was a slight breeze--enough to clear the air of the ever-present dust--which barely shook the sides of the tent. Two Indian servants laid an appetizing meal before their masters. Sir Lionel, elated by his discovery, talked of the city of Sungan. Once or twice he checked himself, as if he feared he was saying too much. But his eagerness was not to be restrained. "The stone proves the existence of Sungan, and gives us a rough idea of its location. Judging from the inscription, the Wusun have clung to their heritage. I think we shall find some survivors in Sungan." "I thought you said the inscription was a form of Sanscrit," objected Gray. "And the Wusun are Chinese----" "Ah, that is just the point." Sir Lionel reared his blond head, like a setter at scent of game. "Sanscrit is an Aryan language. The white race buried here in the Gobi called themselves the Tall People. Wusun is the Chinese translation of that term. Their own written tongue is probably the dialect we saw on the boundary stone, which is Aryan. A clear chain of proof, Captain Gray." "But," the American objected honestly, "my follower, Mirai Khan, has hunted the borderland of the Gobi and he says positively no city is to be seen. The stone is four centuries or more old----" "Mirai Khan," said the girl quickly, "can not see under the sand, can he? He seems to be bent chiefly on stealing horses." Sir Lionel, however, was not to be turned from the discussion which filled his mind. "You forget the sand that Mary mentions, Captain Gray," he retorted warmly. "This is, literally, a sea of sand. And the waves are rising. We are sure that certain towns in the foothills of the Thian Shan have been buried by these waves. You see, the prevailing winds here are from the east. They drive the sand dunes before them. I have noted that the dunes march westward----" "Before you go on, Sir Lionel----" protested the American, remembering his intention to make a clean breast of things. "Not a word, sir. Not another word. Be quiet, Mary"--as the girl started to speak--"I will not be contradicted. It is a scientific fact that the sands march. During the _kara burans_ or black wind-storms they will progress many feet a day. Sungan was built on the great caravan route from China to Samarcand and Persia, many centuries ago. Marco Polo followed this route when he visited the court of Kubla Khan." "But," Gray broke in, "I want----" "I say, it is a fact, sir. Prove the contrary. You can't!" Sir Lionel glared at him hostilely. "I am right. Without doubt, I am correct. Sungan has been buried by the marching sands. Only the towers remain."